1. Field of the Invention
The present invention relates to a sliding unit having a guide rail member and a slider fit in the guide member for back-and forth movement with respect to the guide member, and more particularly sealing means for the sliding unit to keep contaminants including debris, metal cuttings, oil mists and so on, which might occur owing to the back-and-forth movement of the slider, against escape outside the sliding units, and also isolate the sliding unit from foreign materials such as oil mists, dust and dirt which might otherwise enter into the sliding unit.
2. Description of the Prior Art
Sliding units constructed as shown in FIGS. 8 and 9 are conventionally known to work on a diversity of fields including semiconductor manufacturing apparatus, machine tools, various assembling equipments, testing instruments and so on, most of which is expected to work in controlled atmosphere as in a clean room. The prior sliding unit is primarily comprised of an elongated track rail 2 upward opened to have an U-shaped traverse cross-section, a slider 3B accommodated for lengthwise movement in an U-shaped recess 5 opened upward at 27 of the track rail 2, a recirculating-ball screw shaft 4 mating with the slider 3B, and a motor 9 for driving the recirculating-ball screw shaft 4 to turn about its own axis. The recirculating-ball screw shaft 4 is supported for rotation on the track rail 2 at both of a first bearing member 11 installed in an lengthwise end near the motor 9 and a second bearing member 12 installed in the lengthwise opposite end of the track rail 2, which is fastened to any basement by means of suitable fastener means such as screws. The slider 3B fits in the track rail 2 for linear movement through rolling elements running through between the slider 3B and the track rail 2. A bottom 6 and a pair of upright side walls 7A define in combination the recess 5 in the track rail 2. The side walls 7A are provided on their sidewise opposing inner surfaces with raceway grooves 8 while the slider 3B has raceway grooves confronting the raceway grooves 8 on the side walls 7A to define load raceways between them. Rolling elements may run through the load raceway defined between the raceway grooves 8 on the side walls 7A and the raceway grooves on the slider 3B, thereby allowing the slider 3B to move smoothly on the track rail 2.
The slider 3B has a pair of widthwise opposing flanges 13, which are angled upwards to rest thereon an object such as a workpiece table, not shown. The flanges 13 are made with threaded holes 14 for fixture means such as bolts to hold any object thereto. A dustproof cover 15B is attached to the forward and aft bearing members 11, 12 so as to shield the track rail 2 with the exception of sidewise clearances 33 where the flanges 13 are allowed to extend sidewise to move back and forth through there. Thus, the dustproof cover 15B is arranged above the slider 3B and the recirculating-ball screw shaft 4, which constitute in combination a torque-to-thrust conversion system for the sliding unit, thereby keeping the contaminants such as dust and debris against entering into and also coming from inside the track rail 2. The upright flanges 13 of the slider 3B, on which the object to be carried is loaded, extend widthwise outwardly of the tack rail 2 and then turn upwardly so as to be unobstructed with the dustproof cover 15B. The slider 3B has a nut 17 made therein with an internal helical groove that will mate with an external helical groove provided around the recirculating-ball screw shaft 4. The mating of the screw shaft 4 with the nut 17 constitutes a torque-to-thrust conversion system in which the rotation of the screw shaft 4 allows the nut 17 to move linearly lengthwise of the track rail 2. The forward and aft bearing members 11, 12 are mounted on railheads 20 of the upright side walls 7A of the track rail 2. The railheads 20 are finished in parallel with the raceway grooves 8 of the track rail 2.
Sensor rails 22 are disposed on sidewise outsides of the upright side walls 7A of the track rail 2, one to each side wall 7A. The sensor rails 22 are each provided with a limit sensor 23 at any preselected place to sense the associated flange 13 during back-and-forth movement, followed by issuing the detected signal to a controller through a lead wire 24 and a sensor connector 25. The motor 9 is energized depending on any control signal applied through a motor connector 28 to produce a torque transmitted to the recirculating-ball screw shaft 4 via a coupling 30. A fore-and-aft range over which the slider 3B is allowed to travel is defined with stoppers 31, 32 that are secured to the bearing member 11, 12, one to each bearing member.
In Japanese Patent Laid-Open No. 325070/1999, for example, there is disclosed a sealing construction for the sliding unit constructed as stated earlier, in which bellows-like sealing means are installed at the sidewise clearances 33 to keep foreign matter such as dust, debris and so on against entering into and coming from inside the sliding unit through the sidewise clearances 33. The bellows-like sealing means are each composed of at least one sealing member expansible owing to its own elasticity, which is secured to anyone of the confronting lengthwise edges of the upright side wall 7A of the track rail 2 and the dustproof cover 15B to close the associated clearance 33. When the slider 3B travels with respect to the track rail 2 along the clearances 33, the sealing members are easily subject to the elastic expansile and collapsed deformation and thus thrust aside by the action of the moving flanges 13.
Another example of the sealing constructions for the sliding unit made as stated earlier is disclosed in Japanese Patent Laid-Open No. 27235/2001, which is the senior application of the present applicant. With this prior sealing construction, the expansible sealing members are arranged in gaps between the track rail and the dustproof cover in a manner allowing the flanges to travel along the gaps as the slider moves relatively to the track rail. Each expansible sealing member is composed of upper and lower sealing parts that are urged elastically against each other to close the associated gap. When the flange travels along the associated gap, the upper and lower sealing parts are shoved apart from each other at only a region closely neighboring the moving flange to allow it to travel between the sealing parts, with keeping a sliding contact with the opposite surfaces of the moving flange. At the residual regions before and after the moving flange, however, the upper and lower sealing parts are kept in abutment against each other due to their own elasticity. The lower sealing part is made greater in elastic force than the upper sealing part to compensate the influence of gravity. Moreover, the upper and lower sealing parts are made in an elongated configuration that is attached at one lengthwise side thereof to any one edge of the gap and abutted against the counterpart with their own elasticity.
There are also known a conveying system with dust proofing means of the type disclosed in, for example, Japanese Patent Laid-Open No. 187906/2001. The conveying system is made of a rodless cylinder that includes a cylinder tube and a table moving in and out along the cylinder tube. A mounting stage is fastened to the table while a covering member is attached to the cylinder tube. A dustproof member is held between an inside surface of the covering member and any one of side surfaces of the cylinder tube and the mounting stage. The dustproof member may be subjected to elastic deformation in a sidewise direction that is perpendicular to a direction along which the table moves in and out.
With most prior sliding units constructed as stated earlier, nevertheless, any sidewise slits or clearances are left uncovered between the dustproof cover and the track rail to allow the flanges for supporting thereon a workpiece table to travel back and forward integrally with the slider along the clearances as the slider moves back and forth with respect to the track rail. This means many conventional sliding units should not be able to effectively prevent foreign materials such as dust and dirt, and so on from entering into the sliding unit through the clearances and also keep contaminants including debris, metal cuttings, and so on owing to the sliding unit itself against scattering all around through the clearances in the clean rooms where the semiconductor manufacturing machines and the like are installed. To cope with this, various ways constructed as stated earlier have been proposed to keep dust and debris against entering into and escape out of the dustproof cover through slits, clearances and so on. Nevertheless, the major obstacles to all the sealing constructions in which the bellows-like expansible sealing members are installed to close the sidewise clearances and in which the upper and lower expansible sealing parts are urged elastically against each other to close the clearances are necessitating the sophisticated expansible sealing members that are very tough to form them and thus become high in their production cost. Moreover, another problem faced in the expansible sealing members as stated above is how to make sure of more elasticity, with even superior sealing property.
To better deal with the obstacles and problem as stated above, the sealing member as shown in FIG. 7 has been developed, which has been filed by the present applicant under senior patent application in Japan, Japanese Patent Laid-Open No. 206530/2002. The sealing member is convenient to assemble it with the sealing structure in the sliding units and less expensive in production cost. With the sealing structure for the sealing unit in FIG. 7, a sealing member 1A rich in restoring force is secured to the dustproof cover 15A to lie in a clearance that is left opened between the dustproof cover 15A and the lengthwise side wall 7A of the track rail 2. The sealing member 1A constantly closing the clearance 33 between the dustproof cover 15A and the lengthwise side wall 7A of the track rail 2 experiences any deformation of expansion/collapse, with keeping sliding engagement with the associated wing 10A that pushes its way out the sealing member 1A as a sidewise wing 10A of the slider 3A moves back and forth between the sealing member 1A and the side wall 7A. The sealing structure constructed as stated earlier is envisaged to make certain of smooth back-and-forth movement of the slider, helping improve the sealing performance at the clearance 33 and also the durability of the sealing member 1A. Moreover, the sealing member 1A is easy to place correctly it in the associated clearance 33. In the sealing structure shown in FIG. 7, other most parts and components are the same or equivalent in function with those in sealing unit of the present invention, which will be described later. To that extent, the parts and components are given the same reference characters as in the sealing unit in FIG. 3, so that the later description will be applicable.
The present invention, therefore, has as its principal object to refine the sealing structure of the sliding unit disclosed in the Japanese Patent Laid-Open No. 206530/2002. The entire concept of the present invention is to shrink the sealing structure down in size and make it simple in construction in compliance with the sliding units being generally shrinking in size. The major object of the present invention is the provision of a sliding unit in which any clearances to be closed with the sealing members are concentrated on just a limited area on the sealing unit to deal with the need to much more shrink the sliding unit. In particular, the principal object of the present invention is to provide sealing means for a sliding unit, in which at least one projection extends from a slider out of a dustproof enclosure along a clearance left open in the dustproof enclosure to allow the projection to travel back and forth along the clearance, and a sealing member of expansible cellular material is installed to close elastically the clearance, but collapse to allow the projection to move along the clearance, with keeping sliding engagement with the sealing member thereby preventing foreign materials such as dust and dirt, oil mist and so on from entering into the sliding unit and also keeping contaminants including debris, metal cuttings, oil mists and so on owing to the sliding unit itself against escape outside the sliding unit through there into a controlled atmosphere such as clean rooms, laboratories and the like where the semiconductor manufacturing machines and so on are installed.
The present invention is concerned with sealing means for a sliding unit; comprising a guide component including a track rail having a pair of side walls spacing away widthwise from each other and extending lengthwise in parallel with each other, and a slider fit between the widthwise opposing side walls for back-and-forth sliding movement; wherein the guide component is made opened upwardly to provide a clearance defined between lengthwise edges lying in sidewise opposition to each other above the slider, and sealing members of elastic cellular material exhibiting a restoring force are disposed in the guide component, with their sidewise opposing inside fronts coming in abutment against one another to close the clearance; and wherein the slider is provided thereon with a projection to hold thereon an object, which extends through between the inside fronts of the sealing members in a way moving along the clearance with deforming the sealing members in expansion/collapse fashion to constantly keep a close sliding engagement with the inside fronts of the sealing members upon a back-and-forth movement of the slider relatively of the guide component.
In an aspect of the present invention, sealing means for a sliding unit is disclosed in which the projection extends lengthwise of the slider and has forward and aft tapered ends, and a mid-portion left thick in widthwise direction. In another aspect of the present invention, sealing means for a sliding unit is disclosed in which a wear-proof slideway belt is applied on the projection of the slider, with which the sealing member comes into sliding engagement.
In another aspect of the present invention, sealing means for a sliding unit is disclosed in which there is provided a resilient member extending lengthwise of the sealing member to aid the sealing member in speedy recovery from the deformation of expansion/collapse suffered when the projection of the slider moves through the clearance. In a further another aspect of the present invention sealing means for a sliding unit is disclosed in which the sealing member is made of foamed rubber. In another aspect of the present invention sealing means for a sliding unit is disclosed in which the sealing member is coated with a protective skin. In another aspect of the present invention sealing means for a sliding unit is disclosed in which the sealing member has a slim portion made tapered towards the inside front in traverse cross-section, and just the slim portion can be much subjected to an elastic deformation to such extent that the sealing member gets deformed to a substantially quadrangular configuration in cross section as the projection of slider moves with pushing the inside front of the sealing member. In a further aspect of the present invention, sealing means for a sliding unit is disclosed in which a wear-proof slideway belt extending fore-and-aft direction of the sealing member is applied on the inside front of the sealing member with which the projection of the slider comes into sliding engagement.
In another aspect of the present invention, sealing means for a sliding unit is disclosed in which the guide component is made with an air port that is connected with an air line to either suck and expel an atmosphere existing in a space enclosed with the guide component and the sealing members out of the space through there or blow a clean air into the space through there.
In another aspect of the present invention, sealing means for a sliding unit is disclosed in which the track rail is made up of a pair of the side walls and a bottom integral with the side walls in such a way that the side walls rise along widthwise spaced edges of the bottom, thereby forming as a whole a shape of trough.
In another aspect of the present invention, sealing means for a sliding unit is disclosed in which the side walls of the track rail are provided on their widthwise opposing inner surfaces with raceway grooves while the slider is provided on sidewise opposing surfaces thereof with raceway grooves confronting the raceway grooves of the side walls to define load raceways between them, and rolling elements installed in the slider run through the load raceways defined between the confronting raceway grooves, thereby allowing the slider to move back and forth relatively to the track rail.
In another aspect of the present invention, sealing means for a sliding unit is disclosed in which the slider includes a carriage fit in between the side walls of the guide component for sliding movement, and a torque-to-thrust conversion system mounted on the carriage and comprised of a nut mating with a recirculating-ball screw shaft, and wherein the guide component includes driving means to rotate the recirculating-ball screw shaft mating with the nut in the slider.
In a further another aspect of the present invention, sealing means for a sliding unit is disclosed in which the slider has just one projection extending in fore-and-aft direction midway between the widthwise opposing side surfaces thereof, and the guide component is comprised of the track rail, a pair of first covering shells to hold the sealing members therein, one to each shell, the first covering shells being each fastened to the associated side wall, with rising above the side wall lengthwise of the side wall, and end covers attached to forward and aft ends of the track rail, one to each end. In another aspect of the present invention, sealing means for a sliding unit is disclosed in which the covering shell is composed of a covering side extending along the associated side wall, and seal supporters formed integral with the covering side to define a recess lying above the slider to open toward a counterpart that are in widthwise opposition to the covering shell, and wherein the sealing members are installed in the recesses, one to each recess.
In another aspect of the present invention, sealing means for a sliding unit is disclosed in which the slider has two projections that extend lengthwise of the slider, with being spaced widthwise apart from each other, and wherein the guide component is comprised of the track rail, the end covers fastened to the forward and aft ends of the track rail, one to each end, and a second covering shell to hold the sealing members therein, the second covering shell including a pair of covering sides fastened to the side walls of the track rail, one to each side wall, so as to lie lengthwise of the track rail above the side walls, and covering ridges disposed midway between the widthwise spaced projections and fastened at their forward and aft ends to the end covers, and the covering sides and covering ridges being each angled in towards the associated projection at the lengthwise upper edges thereof. In another aspect of the present invention, sealing means for a sliding unit is disclosed in which the covering ridges are made of either an elongated Tee or elongated angles that lie back to back with each other at their legs midway between the projections, with other legs extending in directions opposite towards their associated projections, and wherein the sealing member is made up of a sidewise outside sealing block held in the associated covering side, and a sidewise inside sealing block flanking the associated leg of the covering ridge and held in the associated covering ridge.
In another aspect of the present invention, sealing means for a sliding unit is disclosed in which there is installed a sensor in opposition to any one side of the slider to sense where the slider is. Moreover, in another aspect of the present invention, sealing means for a sliding unit is disclosed in which the sealing member is made up of a major thick portion, and a relatively slim portion reaching from the major thick portion to the projection to mainly afford the deformation of expansion/collapse of the sealing member.
In another aspect of the present invention, sealing means for a sliding unit is disclosed in which a fastener plate is attached to any surface of the sealing member, where the sealing member is mounted to the covering shell. Moreover, sealing means for a sliding unit is disclosed in which the projection has a platform to rest thereon any object including an instrument, part, member, position control table, and so on.
With the sealing structure constructed as stated earlier, the sealing members are disposed on the widthwise opposing inside surfaces of the guide component, one to each inside surface, to close the clearance left opened between the inside surfaces. Upon the back-and-forward linear movement of the slider relatively to the guide component, the projection of the slider can move between the confronting inside fronts of the sealing members in a way deforming the sealing members in expansion/collapse fashion, with keeping the close sliding engagement with the confronting fronts of the sealing members so that the sealing members keep constantly closing the clearance left open between the covering shells. With the sliding unit in which the slider has only one projection, the atmosphere inside the sliding unit is just exposed to the environment at one clearance and, thus, can be kept surely in airtight condition. By the way of contrast, the slider with two projections are effective to make certain of keeping the object on the table steady and also smooth sliding movement of the slider without subject to lean even if the object on the table is lopsided in load.
In accordance with the sealing structure discussed here, it is preferred that the projection is made up of forward and aft tapered ends and a mid-portion left thick in widthwise direction. Moreover, sealing member is preferably made up of a major thick portion fit in the recess defined with the seal supporters of the covering shell composing the guide component, and a relatively slim portion reaching from the major thick portion to the inside front. The sealing member formed as stated just above helps make sure of their natural deformation in expansion/collapse fashion with keeping good closing condition, when the projection of the slider travels in a way shoving the sealing members aside. With the sealing structure of the present invention, thus, foreign materials such as dust and dirt, and so on are kept against either entering into or coming from inside the sliding unit through the clearance between the sealing members lying on the seal supporters of the covering shells. For example, debris, metal cuttings, and so on caused owing to the back-and-forth movement of the slider are kept against scattering all around through the clearance in the clean room, which will be thus maintained in any desired cleanliness. In addition, as the foam rubber for the sealing member is made in a simple quadrangular shape in traverse cross-section, rather than any sophisticated shape and structure that might introduce costly production requirements, the sealing member devised in the present invention can be much reduced in its production cost and also is easy to apply it to any clearance left open between the sidewise opposing surfaces of the guide component.
In accordance with the sealing structure of the present invention, the sealing member has resilient member extending lengthwise on the side making a sliding contact with the projection of the slider to aid the sealing member in speedy recovery from the deformation of expansion/collapse suffered when the projection of the slide moves in a way pushing the sealing member aside. Even if the sealing member were subjected to deterioration due to aging, for instance, even when the projection of the slider were actuated after stood idle for a long period, moreover, any spring force of the resilient member would aid the sealing member to immediately restore its initial shape from the deformation of expansion/collapse, without leaving signs of the associated projection on the sealing member. Thus, it will be expected that the spring force of the resilient member works to improve the response of the sealing member to the deformation of expansion/collapse, thereby raising the close engagement of the sealing member with other surfaces to make sure of high sealing performance.
With the sliding unit with the sealing structure constructed as stated earlier, the projection extending upward above the top of the slider is to rest thereon any load or object to be carried including parts, instruments, members, and so on for production machines. The sliding unit with the sealing structure of the present invention, although limited to just a small weight in load capacity to be carried, is suitable to shrink it down to the size most conformable to parts, instruments, table and so on, which weigh less enough to be carried on, for example semiconductor manufacturing equipment, position control table and the like. The sliding unit of the present invention is most suitable to work well on the machines that need the sliding unit much less in sidewise dimension, as is the case, for example in assembling machines in which many tables have to be placed one upon another within a limited space. Further, the sliding unit according to the second embodiment of the present invention has two projections extending upwards above the slider, which tolerate the sliding unit bearing the more massive load than in just one projection. Moreover, the sliding unit of the present invention, because the slider does not have any wings extending sidewise out of the sliding unit as in the prior sliding unit, is made much slim in widthwise dimension, compared with any types of the prior sliding unit.
The sealing member of the present invention is made in a quite simple shape, for example a substantially trapezoidal shape composed of a thick portion of quadrilateral in cross section and a tapered slim portion. This means that the sealing members are most easily installed in the recesses between the seal supporters of the covering shells, one to each recess, with their confronting inside fronts extending towards each other out of the seal supporters into abutment against one another. Moreover, the sealing member of such simple shape as stated earlier is infinitesimal in the likelihood of causing any irregular deformation in itself, helping realize improvement in sealing performance, with even inexpensive in production cost.
With the sealing structure of the present invention, it is said that the atmosphere inside the sliding unit enclosed with the guide component and the covering shells proves substantially airtight, except that it is exposed to the environment at just a tiny area where the projection extends outside through between the lengthwise fronts of the sealing members coming abutment against each other. Thus, the sliding unit is only needed to experience a minor amount of suction even when air existing inside the sliding unit has to be sucked out to expel debris, metal cuttings, oil mist and so on owing to the sliding unit itself. Thus, it is said that the sliding unit of the present invention is so constructed as able to easily provide the high cleanness-assured working environment. That is to say, the sealing structure of the present invention makes certain of keeping the contaminants including debris, metal cuttings, oil mist and so on, which might occur owing to the sliding unit itself, against scattering outside the sliding unit and also most reducing the occurrence of the debris ever realized. Consequently the sealing structure of the present invention serves good sealing function and there is no occurrence of any obstacle in the clean room where, especially, the semiconductor manufacturing machines are installed. Further, the sealing construction using the sealing member of porous substance such as foam rubber is effective to protect the sliding unit against an invasion of foreign matter such as dust and dirt through the clearance in the sliding unit.
In case where the sealing structure of the present invention is availed in a bad environment full of a cloud of dust, it will be appreciated to force a clean air in the reverse direction into the inside of the sliding unit through the air port that has been originally envisaged to expel the contaminated air out of the sliding unit, blowing the clean air out through the clearances or gaps in the sliding unit, thereby keeping the foreign matter such as dirt and dust against entering inside the sliding unit, which might otherwise ruin the sliding ability of the sliding unit in itself, and making sure of increasing the durability of the sliding unit. Usage as stated just above is most effective in the worst-working environment including woodworking sites full of sawdust, working shops to cut, grind and polish ceramics, and so on.
The above and other related objects and features of the present invention will be more apparent to those skilled in the art from a reading of the following description of the disclosure found in the accompanying drawings and the novelty thereof pointed out in the appended claims.